“Bob Menendez is running the DSCC during a very difficult time a more difficult time than when I was running it,” Schumer told the shell-shocked Democratic caucus, according to a person in the room. “We all ought to get behind him and realize it’s not 2006 or 2008.”

That Schumer felt compelled to take the extraordinary step of defending his successor showed just how fast Menendez’s stock has fallen following a series of devastating setbacks, culminating with this week’s surprise retirement announcement by Sen. Evan Bayh (D-Ind.).

It also represented Schumer’s recognition that many in the party have been unfavorably comparing Menendez’s tenure to his own two successful terms at the helm of the DSCC, which resulted in a historic net gain of 14 Democratic seats.

“Chuck – wow – he would call all the time, three, four times a week when he needed something, but I don’t ever hear from Menendez unless I initiate the contact,” said a Washington-based donor who has bundled tens of thousands of dollars in contributions to the committee.

“You just don’t have the same level of energy from Bob, he just doesn’t push you like Chuck would,” the source added.

“And that makes it a lot easier to say no.”

Many donors are still saying yes, of course. DSCC officials tell POLITICO that the loss of the Massachusetts race hasn’t hurt fundraising, and the committee had its best January ever, raking in $5.1 million. The committee now has $12.9 million in cash in the bank, despite spending at least $2.5 million in the unsuccessful attempt to hang on to Kennedy’s old seat.

And no one claims Menendez is entirely to blame for Martha Coakley’s humiliating defeat in Massachusetts, the retirements of Bayh and North Dakota Democrat Byron Dorgan and Beau Biden’s decision to skip the Delaware Senate race. They cite any number of external factors that have dimmed the party’s prospects: the tanking popularity of President Barack Obama and his policies, the inevitability of Democratic letdown after four years of historic successes and, above all, the lousy economy.

But many Democrats also wonder if Menendez’s lower-octane management style fits the desperate times – and they fret that the party, which got its 59th and 60th seat on his watch, will now plunge back into the minority.

“He’s very good at strategy and he’s very smart, but he’s sort of aloof, and that’s not what we need right now,” said one Democratic consultant, who spoke on condition of anonymity.

Former Sen. Bob Kerrey (D-Neb.), who chaired the DSCC for two terms in the late 1990s, praised both Schumer and Menendez but said the New Jersey Democrat can’t match his predecessor’s maniacal drive and intensity.

“Nobody wins that comparison - nobody wins that comparison,” said Kerrey of matching up Menendez against Schumer “Chuck is the best.”

In fact, no other senator wanted to succeed Schumer, who stepped down in 2009 – fearful of a Democratic debacle in the midterms, other Democrats heeded the never-follow-an-animal-act logic of political succession.

Menendez, a powerhouse fundraiser with strong Wall Street connections, said he took one for the team – and only after Senate Majority Harry Reid (D-Nev.) asked him repeatedly to do it. He bristles at any comparisons to Schumer.

“Listen, it’s nice to have a cycle when you have George W. Bush and eight years of failed policies and have Barack Obama as a candidate,” Menendez told POLITICO.

“If someone wants to compare that cycle with mid-term election history and say it’s apples to apples, I guess they’re free to do so,” he added. “The bottom line is it’s clearly not the same.”

But insiders are increasingly skeptical of Menendez’s political management style – cool, strategic, disciplined, privately caustic and publicly cautious. They pine for the days of Schumer’s control freak-on-Red-Bull tenure, with his 15-hour days and relentless badgering of donors, potential candidates and incumbents.

Menendez's low-key approach has come in useful in some instances. Right before Sen. Christopher Dodd, who was headed for defeat, decided not to run for reelection, Menendez took him out to dinner and told him, "I'm going to be with you, I'm going to have your back, but I'm telling you that I'm very nervous," according to a staffer familiar with the conversation.

Menendez was caught flat-footed by Bayh’s surprising decision, but he wasn’t alone; Bayh, who has few close friends in the Senate, kept his plans secret from the White House and from Reid, who has an especially chilly relationship with the Indianan.

Schumer, Menendez and White House officials have known Bayh was wavering since last fall – and were aware that his apprehension increased with entry to the race of former GOP Sen. Dan Coats. Both Schumer and Menendez continued to lobby Bayh, even though he led them to believe he planned to stick it out.

“We’ve known for a while the Sen. Bayh was considering his options, including retirement,’ said Menendez, who was reluctant to discuss details of the conversations. “We have been actively involved in trying to make sure that he chooses to run. I’ve had multiple conversations with him… We did a full-court press there.”

The DSCC, at Menendez’s request, unleashed a wave of opposition research highlighting Coats’s lobbying career, in part to buck up a rattled Bayh and convince him the DSCC was willing to hit his opponents hard, according to people familiar with the situation.

For all the angst, DSCC officials insist they are in reasonably good shape in a terrible political environment and the situation would be far worse if Menendez hadn’t recruited top-tier candidates in Louisiana and North Carolina.

And, despite a sour economy, many Democrats – including Reid, Blanche Lincoln (D-Ark.) and Michael Bennet (D-Colo.) -- hold significant fundraising leads over their front-running GOP challengers. Many of the party’s non-incumbent candidates are also sitting on cash piles.

But Menendez and the DSCC also face potentially costly races in California, New York and Illinois, all very expensive media markets. And with Menendez’s efforts tied down defending incumbents – which is the primary mission of the DSCC, after all – he will have less to spend to fund challengers in GOP-held seats.

“The challenge for Bob is that he has to raise money for challengers, and that’s hard,” Kerrey, the former DSCC chairman, said. “He’s got two senators running in New York, one senator running in California. He has very expensive media markets that he has to cover … There aren’t very many states where he doesn’t have to spend money.”

Menendez, known to have sharp elbows in private, has been one of the few Democrats unwilling to point fingers for Massachusetts, refusing to fire back at his critics in the White House.